AAON M2-036 - Manual (Page 40)

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Only clean ACR tubing should be used.
Piping should conform to generally accepted
practices and codes.
The air handling unit coils are pressurized.
The copper caps must be punctured to
permit a gradual escape of the pressure prior
to un-sweating those caps. Immediately
couple the tubing to the indoor unit to avoid
exposing the coils to moisture. A properly
sized filter drier is furnished in the
condenser. When making solder
connections, make sure dry nitrogen flows
through the lines, when heating the copper,
to prevent oxidization inside of the copper.
When piping is completed
interconnecting piping and air handling
unit must be evacuated to 500 microns or
less and leak checked. Condenser shutoff
valves can then be opened to allow
refrigerant to flow to the air handling unit.
Thermal expansion valve bulbs should be
mounted with good thermal contact on a
horizontal section of the suction line close to
the evaporator, but outside the cabinet, and
well insulated.
Refrigerant lines should be fastened and
supported according to local codes.
Unit should be charged based on
determination of sub-cooling and superheat.
See Adjusting Refrigerant Charge section
for more information.
Refrigerant reheat coil for the modulating
hot gas reheat option is factory installed.
Liquid line receiver should be installed at
the condensing unit. Care must be taken not
to cross circuits in reheat systems.
Modulating Hot Gas Reheat Piping:
1. Run a hot gas reheat line from the
condensing unit and connect it to the inlet of
the stub-out on the reheat coil. The inlet
connection is the top (or highest) stub-out of
the reheat coil. Connect the hot gas line
from the outdoor unit to the upper stub-out
connection of the reheat coil.
2. Run a liquid line from the discharge of the
reheat coil through a tee connection. Run a
liquid line from the condenser, through a
check valve to the other side of the tee. Run
a liquid line from the tee to the liquid line
stub-out of the evaporator coil.
3. Run a suction line from the evaporator
coil outlet stub-out to the condensing unit.
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure:
1. Minimum pressure drop, and
2. Continuous oil return, and
3. Prevention of liquid refrigerant slugging,
or carryover
This section is for information only
and is not intended to provide all
details required by the designer or
installer of the refrigerant piping
between the condenser or
condensing unit and the air handling
unit. AAON is not responsible for
interconnecting refrigerant piping.
Consult ASHRAE Handbook –
Refrigeration and ASME Standards.
CAUTION
Line sizes must be selected to meet
actual installation conditions, not
simply based on the connection sizes
at the condensing unit or air handling
unit.
CAUTION